Optical transmission networks, including Synchronous Digital Hierarchy (SDH), Synchronous Optical Network (SONET) and Optical Transport Network (OTN), are traditionally designed for transferring voice service. With the rapid development of data service, the proportion it occupies in the transmission traffic of an existing optical network becomes larger and larger, bandwidth demand on the transmission network becomes greater and greater, and the time for service provision is required to become shorter and shorter. As a result, existing network architecture and networking modes are impacted. To meet requirements of data service transmission, the network's topology needs to evolve from a traditional ring network to a mesh network in domination, and the provision mode of network connection service needs to transit from a permanent connection for static provision to a signaling-based soft permanent connection and switched connection in domination. Such a novel optical transmission network is referred to by the International Telecommunication Union—Standardization Sector (ITU-T) as Automatically Switched Optical Network (ASON). A control plane is introduced into the ASON for setting up, modifying and maintaining a network connection and recovering the connection in case of a network failure. One of signaling methods in the ASON is to employ Generalized Multi-Protocol Label Switching (GMPLS) developed by the Internet Engineering Task Force (IETF).
In a mesh network, to ensure that network connection service can be recovered in case of a network failure, a standby recovery path needs to be established for a working path of the connection. The following are strategies to establish a recovery path.
1) A recovery path is pre-established, in other words, a failure-independent recovery path is established in advance for a working path before a network failure occurs (when two paths are failure-independent, it means that these two paths will not be interrupted simultaneously due to the same network failure; failure-independency of two paths requires that the two paths should neither pass the same link nor pass the same Shared-Risk Link Group (SRLG)). An advantage of such a protection mode lies in that the time for recovering is short, usually less than 50 ms; however, its disadvantages are that the bandwidth occupation is high and the resource utilization is low.
2) A recovery path is computed in advance and network resources are reserved in a shared mode; after a network failure occurs, the recovery path is established dynamically. This protection mode is usually referred to as “shared mesh network recovery”. Advantages of such a protection mode lie in that, resources can be reserved by reasonably planning a working path and a recovery path required by each network connection and the resource utilization can be improved by resource sharing of the recovery path. However, the time for recovering is longer than that in the recovery path pre-establishment mode, usually about 200 ms or longer.
3) A protection path is established on demand, in other words, a recovery path is computed again after a network failure occurs, and then the connection is tried to be recovered. An advantage of this protection mode lies in that any unpredictable network failures such as multiple network failures can be supported. Its disadvantages are that, the connection recovery cannot be guaranteed because no resource reservation is performed in advance, and its reliability is poor, and the time for recovering is much longer, usually several seconds.
Because the protection mode of shared mesh network recovery is both of high reliability of connection recovery and high resource utilization, it is regarded as a very effective method for service protection and recovery.
At present, a technical solution for recovering a shared mesh network is proposed in the field. In this technical solution, both a working path and a recovery path are established using a Resource ReSerVation Protocol-Traffic Engineering (RSVP-TE) protocol specified in RFC3743 specifications, a “PROTECTION” object is added by extending the protocol, and one bit in the object (referred to as “bit S” below) is used for indicating a recovery path of a shared mesh network. If the bit S is set as 1, the control plane only reserves resources but does not establish any cross connection. After the working path is interrupted due to a network failure, this bit is set as 0, and the control plane starts a cross connection and establishes a recovery path using the reserved resources; moreover, both the resource reservation and the cross connection establishment are realized through signaling interaction. Specifically, it includes the following processes.
1) A network ingress node of network connection service (referred to as “ingress node” for short) first determines source routing information of a working path and establishes the working path via a signaling protocol.
2) The ingress node determines source routing information of a recovery path, and “establishes” the recovery path via signaling. The difference from the establishment of the working path lies in that the bit S in the establishment signaling of the recovery path is set as 1, and each node on the recovery path only reserves link resources and does not establish any cross-connection. Therefore, the recovery path is not connected when the working path is in a normal state. During the whole life cycle of the network connection service, signaling sessions of the recovery path and signaling sessions of the working path both need to be maintained.
3) After the ingress node finds that the working path is interrupted due to a network failure, it sets the bit S in the signaling of the recovery path as 0. This modification is delivered station by station along the nodes on the recovery path via signaling message refresh. Each node that is passed establishes a cross connection of the recovery path using the reserved resources. The ingress node and an egress node further switch the network connection service from the working path to the recovery path for transmission.
During making the invention, the inventor finds the following issues.
The existing RSVP-TE protocol needs to be extended in the above technical solution, so it is complex to implement the solution.
In this technical solution, a signaling procedure needs to be started in advance when resource reservation is performed for the recovery path, and the signaling procedure continues from the beginning of the working path establishment to the ending of services on the working path. As a result, the load of the control plane in the signaling maintenance connection state is raised, the communication traffic of the data communication network is increased, and a lot of network resources are required to be consumed.